1. Field of the Invention
The present invention relates generally to an optical switch, and more specifically to an optical switch for switching between multiple input or output optical pathways.
2. Description of the Related Art
Optical switches are widely deployed in optical networks to provide functions such as light path routing, protection switching, and system performance monitoring. The switching function is generally achieved by mechanically moving fiber or other bulk optic elements using stepper motors, controlled actuators or electrical relays.
FIG. 1 shows a typical prior art 1×2 optical switch configuration. The optical switch 100 is shown in a first position, whereby an input optical signal 102 is directed to a first output optical waveguide 121. FIG. 2 shows the prior art 1×2 optical switch of FIG. 1 in a second position. The optical switch 100 is shown in a second position, whereby the input optical signal 102 is directed to a second output optical waveguide 122.
A 1×N optical switch (with N>2) is usually realized by cascading multiple 1×2 optical switches. FIG. 3 shows a typical cascaded 1×4 optical switch 300 of the prior art where three 1×2 switch elements are utilized. Within a first optical switch 310, an input optical signal 302 is directed along either a first optical pathway 314 to a second optical switch 320 or along a second optical pathway 316 to a third optical switch 330. The second optical switch 320 directs the input optical signal 302 between first and second output optical waveguides 321, 322, while the third optical switch 330 directs the input optical signal 302 between third and fourth output optical waveguides 333, 334.
With the typical cascading technique of the prior art, a 1×N optical switch consists of N−1 1×2 individual optical switching elements. As N increases, the number of the 1×2 optical switching elements increases linearly. For example, the 1×4 optical switch of the prior art shown in FIG. 3 consists of three 1×2 optical switching elements. A 1×8 optical switch of this type would require seven 1×2 optical switching elements, a 1×16 optical switch would require fifteen 1×2 optical switching elements, and so forth. These designs result in increased bulk and complexity, especially as the size of the optical switch increases. Insertion losses also accumulate rapidly as the number of cascading levels increase. As such, cascading 1×2 optical switches are not an optimal solution for high port-count 1×N optical switches. Alternate non-cascading type optical switches of the prior art also require N−1 optical switches or have switching elements that move between more than two switching positions. The number of redundant switching elements adds to the costs of these devices and results in overly complex switching logic. Further, moving between more than two switching positions requires additional time and strict alignment tolerances, making these types of switches unsuitable for low-cost or high-speed applications.
Therefore, there is a need for an improved optical switch which overcomes the shortcomings of the prior art described above.